Active implantable cardiac devices include such systems as cardiac monitors, pacemakers, implantable defibrillators and cardiac resynchronization devices, among others. Such systems typically include implantable electrodes coupled to circuitry for sensing and analyzing electrical signals. Some systems are designed with multiple sensing electrodes to define multiple sensing vectors. For example, implantable transvenous and subcutaneous systems for monitoring and treating cardiac conditions are disclosed in U.S. Pat. No. 7,623,909, titled IMPLANTABLE MEDICAL DEVICES AND PROGRAMMERS ADAPTED FOR SENSING VECTOR SELECTION, the disclosure of which is incorporated herein by reference. The '909 patent discusses methods for selecting a default or primary sensing vector from among several available sensing vectors. Some examples allow for selection of primary and secondary vectors in the '909 patent.
Additional examples of implantable systems with multiple sensing vectors can be found in U.S. Pat. No. 8,200,341, titled SENSING VECTOR SELECTION IN A CARDIAC STIMULUS DEVICE WITH POSTURAL ASSESSMENT, U.S. Pat. No. 7,392,085, titled MULTIPLE ELECTRODE VECTORS FOR IMPLANTABLE CARDIAC TREATMENT DEVICES, and U.S. Pat. No. 5,331,966, titled SUBCUTANEOUS MULTI-ELECTRODE SENSING SYSTEM, METHOD AND PACER, the disclosures of which are incorporated herein by reference. Continuing enhancement of such systems is desired.